Electric apparatus for cleaning oil



Feb. 20, 1951 G. w. PENNEY El AL ELECTRIC APPARATUS FOR CLEANING OIL 2 Sheets-Sheet 1 Filed July 1, 1948 Source INVENTORS Gay/0rd M Penne y and eorg'e Mflerw/f BY ,a 1 MM ATTORNEY Feb. 20, 1951 e. w. PENNEY ET AL ELECTRIC APPARATUS FOR CLEANING OIL Filed July 1, 1948 2 Sheets-Sheet 2 INVENTORS 3. h Me %A if @m W6 Patenteci Feb. 20, 1951 ELECTRIC APPARATUS FOR CLEANING OIL Gaylord W. Penney and George W. Hewitt, Pittsburgh, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application July 1, 1948, Serial No. 36,393

3 Claims.

From one aspect, this invention relates to an electrostatic precipitator means for efliciently removing particulate matter from a flowing gas, especially air to be breathed, the particulate matter being any of the particles generally designated in the art as dust. From another aspect, this invention relates to a cleaning system in which a suitable liquid such as oil is recirculated in a path including a dust-bearing medium that holds dust of a type found in air. During the recirculation, the oil removes such dust from the dust-bearing medium and becomes contaminated with such dust. The cleaning system includes a liquid-cleaning container having electrostatic liquid-cleaning means for electrostatically precipitating such dust from the liquid so that clean liquid is always available for recirculation in the cleaning system. From still another aspect this invention relates to a novel container fo oilcleaning. The container is divided by an essentially vertically extending wall-means into sections or portions in oil-commingling relation, a first of which contains an electrostatic oil-cleaner, and a second of which contains clean oil which cannot be readily contaminated with dirt removed from the oil by the oil-cleaner, so that a supply of clean liquid can be taken from such second section or portion.

In order to illustrate the various aspects of our invention, preferred embodiments are shown in conjunction with a suitable type of electrostatic precipitator which cleans a gas containing dust by charging the gas-borne dust particles and precipitating the charged particles. Specifically the electrostatic precipitator chosen for the purposes of describing the invention utilizes the teachings of G. W. Penney Patent No. 2,129,783, granted September 13, 1938. However, our invention, in some of its aspects, may incorporate other forms of electrical dust precipitators or dust-bearing mediums.

The precipitator shown in the aforesaid patent is especially useful fo cleaning air. The aircleaning is accomplished by first passing the dustcontaining air through an ionizing zone or chamber in which dust particles in the air-stream are charged, and then passing the air through a separate precipitating dust-collecting zone or chamber in which charged dust particles are separated from the air-stream by being precipitated onto oppositely charged dust-collecting members in the form of plates. The air-cleaning parts of our preferred embodiments are preferably constructed and operated as taught in the aforesaid patent so that efficient air cleaning is obtained with especially low consumption of electrical energy, and negligible generation of ozone or oxides of nitrogen; features which are especially desirable in electrical precipitators for cleaning air to be breathed.

The degree and length of time that a dust particle electrostatically precipitated from air or other gas will cling to a dust-collecting plate depends on several factors, some particles clinging for a long time and others for a very short time. In many instances, it has been found desirable to add a substance to the dust-collecting plates which will make the precipitated dust particles cling or adhere to them better or longer, the plates being washed occasionally to remove the accumulated or collected dirt or grime from the plates. Ordinary lubricating oil is useful for such a purpose, although any other suitable liquid which has the quality of holding dust and of making the dust adhere to the plates can be used; but it is desirable to use a non-odorous insulating liquid having a low vapor pressure, a high flash point and a suitable viscosity when the gas being cleaned is air to be breathed. These factors depend, of course, on the particular construction of the particular precipitator device, the type of dust that is expected to be precipitated and the character of the gas being cleaned. A good quality motor oil and other oil or oil-mixtures of suitable characteristics are usable with air-cleaning dust precipitators and other dust-bearing apparatus. Such liquids are herein embracively designated as oil.

A gas-purifying electrical precipitator utilizing oil washing of the dust-collecting plates is shown in G. W. Penney Patent No. 2,347,709 of May 2, 1944. This precipitator is automatic in its operation and has an oil container or reservoir from which oil is automatically pumped at chosen intervals for predetermined lengths of time to wash the dust-collecting plates and also the ionizing parts of the ionizing zone. During washing operation of these parts, the accumulated dust or dirt which has been withdrawn from the air is washed off the dust-collecting plates by the flushing oil. After the washing operation, the flushing oil drains from the dust-collecting plates and leaves a thin film of oil on them for causing subsequently deposited dust to adhere. However, after one or several washings, the oil in the reservoir becomes heavily dust-laden with washed-off dust, a large part of which is composed of such small particles that they do not settle down between the washing intervals remeans 3 quired for the most efiicient operation of the precipitator.

It is among the objects of our invention to provide a self-contained electrical precipitator device having means for automatically, safely, efficiently and economically washing gas-purifying parts of the precipitator device with clean oil.

An important object of our invention is to improve the efllciency of an electrostatic dust precipitator of a type described, for cleaning air to be breathed, by novelly coordinating an electrostatic oil-clean'ng means therewith for cleaning the oil used to wash the dust-collecting plates and other parts of the dust precipitator.

Another object of our invention is to provide a complete system, such as one containing an aircleaning electrical precipitator of a type described, in which the electrostat'c oil -cleaning means is energized by a voltage which can be derived from the customary power-pack, or limited energyvoltage conversion means, which also supplies the energizing voltages for the dust-chargbreathed.

Another principal object of our invention is to provide an oLl-storage or reservoir with means for cleaning substantially all of the oil in the tank or reservoir by electrostatic means which electrostatically removes from the oil the dust therein of a type found in air. In some forms of our invention, the electrostatic oil-cleaning occupies but a small fraction of the total volume of the tank or reservoir so that it is practical to clean large bodies of oil stored in the tank or reservoir with equipment of a reasonable size. Preferably, in this use of our invention, the oil-cleaning means comprises oppositely charged electrode-means occupying but a small portion of the storage tank or reservoir which holds the oil. In a preferred embodiment, the electrode-means establishes an electrostatic field only in a small part of the tank, but the electrostatic action is sufiicient I to cause a drift or migration of oil in the tank through the electrode-means, so that substantially all of the dirt in all of the oil in the tank is removed and is confined to the part of the tank associated with the oil-cleaner.

In general, a container, tank, or reservoir embodying our invention has a distinct oil-space which contains clean oil. This clean oil is kept separated from oil and dirt in the oil-cleaning space of the tank, and can be withdrawn for circulation to any suitable dust-bearing medium which is to be cleaned by washing with such oil. The clean oil takes dust from the dust-bearing medium and thereby becomes contaminated. The contaminated dust-laden oil is returned to the tank or reservoir where it is electrostatically cleaned so that it can be re-used eifectively.

The electrode-means for cleanin the oil preferably comprises a plurality of spaced alternately relatively insulated and uninsulated oppositely chargeable precipitating members which are preferably but not necessarily fiat plates. In the preferred apparatus, with oil originally containing dirt, such as found in air, the dirt removed from the oil forms a heavy thick mass on the flat plates which eventually falls or slides down the plates and can be separately collected. For lack of a better name, we desigmate as sludge this heavier thick mass of oil in which the dirt concentration has been increased. This collected sludge may have a consistency similar to that of heavy mud, tending towards a natural level when alone, but not always achieving this result.

The objects, features, advantages and applications of our invention are numerous, and generally embrace those hereinbefore indicated, and others which will be apparent or discernable from the following description which is to be taken in conjunction with the accompanying drawings.

The drawings are schematic and not necessarily to scale. In some of the figures, details and features have been omitted in the interests of clarity and brevity. In the drawings:

Figure 1 is a vertical sectional view of an electrostatic dust precipitator system embodying our invention;

Fig. 2 is a sectional view taken substantially along the line II-II of Fig. 1;

Fig. 3 is a wiring diagram indicating the manner in which the different electrical parts of the system can be energized;

Fig. 4 is a fragmentary. sectional viewshowing the manner in which the plates of the oil-clean ing means in the oilstorage tank of Fig. 1 may be assembled;

Fig. 5 is a vertical fragmentary sectional view of a modified form of sludge segregating means for an oil storage tank;

Fig. 6 is a view, partly diagrammatic and partly in section, of a modified form of our invention;

Fig. 7 is a sectional view substantially along the line VII-VII of Fig. 6, showing, in elevation, a member for dividing the oil container into portions or sections;

Fig. 8 is a vertical sectional view of a modified form of a storage tank and oil-cleaning means;

Fig. 9 is atop plan view of the modification shown in Fig. 8;

Fig. 10 is a vertical sectional view taken substantially on the lines X-X of Fig. 8; and

Figs. 11 and- 12 are vertical sectional views of further modifications.

Referring more particularly to Figs. 1 and 2, a form of electrostatic gas-cleaning dust precipitator is shown for cleaning air to be breathed which comprises a conduit means through which air to be cleaned passes, the conduit means including an intake duct 2 and a vertical air-cleaning cabinet duct or treating chamber 4. In the embodiment shown, the treating chamber 4 is provided with an outlet discharge 6 for cleaned air. The cleaned air may be discharged directly into the premises being air conditioned, or into other conduits whichguide the cleaned air to any desired location. The air flow is in the direction indicated by the arrows, being propelled by a blower means comprising a propeller I driven by a blower motor 8.

In passing through the treating chamber 4, the air-borne dust particles first pass through an ionizing zone comprising a plurality of spaced elongated transversely-curved electrodes ill, in the form of tubes or parts of tubes, and ionizing electrodes or wires I2 parallel to and between each pair of curved electrodes, the electrodes being arranged in a plane transverse to the air flow. The curved electrodes IO and the ionizing wires 12 are relatively insulated, as iscustomary in apparatus of the type described. The electrodes H] are preferably grounded, and are hereinafter called ground electrodes for identification. Spaced parallel vertical grounded plates l4 interleaved with spaced insulated plates l6 comprise the dust-collecting zone H.

The bottom of the treating chamber 4, below the discharge opening of the inlet duct 2, is provided with a removable drain pan or basin H; which has a bottom that slopes downwardly to an oil-outlet spout 20. A metal casing 22 is arranged about the .lower end of the treating chamber 4 and carries therein, an oil container or reservoir in the form of an oily tank 26. Oil for cleaning the dust-bearing precipitating members in the treating chamber 4 is carried in this tank.

The tank is provided with a removable top or cover 28. The top 28 is below the basin 3, and has a pipe 35 below the spout 20. The spout 2E) fits into the pipe 30. The tank cover 28 is of a heat-resistant material, such as, for example, asbestos backed sheet metal. By segregating the oil in the tank from the air stream as much as possible, fire hazards are, of course, greatly reduced. By covering and substantially enclosing the oil in a container, reservoir or tank, there is little chance of the .oil burning, if it be inflammable or combustible, except under extreme conditions.

A pipe 32, which may be flexible, is connected to the intake of an oil pump 35. In the par-- ticular embodiment being described, the intake end of this pipe may terminate at a point about or less from the bottom of the tank. The pump at is driven by an electric motor 35, through variable-speed gearing (not shown) if desired. When the pump is operating, oil from the tank is pumped through a clean-oil conduit comprising the pipe 32 and extending to an oil-distribut ing nozzle means 36 in the treating chamber 4. The nozzle means 38 is located above the dustcollecting zone ii.

In the operation of the structure thus far described, the blower motor 8 is preferably deenergized during energization of the pump motor 35, and conversely, the pump motor 35 is deenergized while the blower motor 8 is operating. Assuming that the blower motor 8 is energized, air will be blown first through the inlet duct 2 and then successively through the ionizing zone and dustcollecting zone. In passing through these zones, airborne dust is first charged and then precipitated or collected on the precipitating plates of the dust-collecting zone, the plates thereby comprising a dust-bearing medium of the treating chamber 1. Usually some dust also collects on the members of the ionizing zone, and also on inside parts of the walls of the treating chamber 4. After a suitable interval of time, the blower motor is deenergized and the pump motor 35 energized so that oil in the tank or reservoir 26 is pumped through the treating chamber 5, flowing over the parts of the dust-collecting zone and ionizing zone, thereby washing oil the layers of collected dust in the chamber 4. The washing oil is caught in the basin i8 and immediately flows through the drain spout 26 into the tank 26, through the delivery pipe 3%. Oil deflector baffles 38 deflect oil into the basin.

When it is believed or observed that the precipitator parts are sufliciently clean, the pump motor 35 is deenergized, and it is desirable, with a dust precipitator of the type described, to leave both motors 8 and 35 idle for a short time to permit excess oil to drain from the dust-collecting plates. However, because of the sticking quality of the oil, the plates will retain a layer or film of oil over their surfaces, which will cause any dust later precipitated or deposited on them to adhere better, so that there is very little, if any, subsequent blowoil of the precipitated dust.

In systems of this kind, in which it is desirable to Wash down the dust-collecting plates because of the heavy dust concentrations of the air being cleaned, or for other reasons, the washing oil removes dirt having very fine dust particles. 'Such dirt does not settle out of the oil during the intervals between plate washings, which may be as'much as twenty-four hours or more, but is usually less. Unless cleaning means for more quickly cleaning the oil is provided, the plates would, after one or a few washings, be washed with dirty oil and also coated with dirty oil. To avoid this condition and to keep the washing oil clean, we have devised an oil-cleaning means which segregates the washed-off dirt from the oil so that cleaned oil can always be made available for washing and coating the dust-collecting plates.

In accordance with our invention, We support an electrical oil-cleaner 3: 5 in the container, reservoir or tank 25. In the preferred form in which the oil is not used for relatively long periods, the oil-cleaner occupies but a small fraction of the volume of the tank and consequently is relatively small in comparison with the tank. The oil-cleaner of the embodiment being described comprises a series of spaced electrically grounded flat plates fill between which are dis" posed a series of somewhat smaller insulated fiat plates .2. The plates are secured together by an insulating clamping means which comprises one or more insulating tierods 45 passing through suitable aligned holes in the upper corners of the plates. Insulating spacers G6, slid on the tie rods, keep the plates properly spaced. The assembly can be handled as a unit. In an assembly the edges of the insulated plates 42 are inward of the edges of the grounded plates 48. The assembly can be supported in the tank 26 in any suitable manner, as for example, by means of metal hanger hooks 48 which are connected to ground and hang over the edges of the tank, and support the assembly below the top 28 of the container or tank 2'6. Secured to the hooks #38 are small metal straps 5e, fastened to the tops of the grounded plates 40. The size of the oilcleaner plates is such that their vertical edges, in this case, are spaced from the adjacent vertical sides 5 and 56 of the tank, and their bottom edges are above the bottom of the tank to provide a sludge-receiving section or portion below the oil-cleaner.

The oil tank 28 is provided with a wall of any suitable shape or form which is positioned so as to extend in an essentially vertical direction in the tank so as to provide at least a pair of segregated or distinct portions or sections therein.

One of these portions,provides an oil-spacefrom which clean oil can be taken from the container or tank. In the embodiment shown in Fig. 1, this wall is in the form of a solid partition 58 which is fixed in the tank 25 and extends for the full width of the tank, between the side walls 54 and 56. The partition 58 divides the tank into a plurality of sections, compartments or portions, comprising a principal compartment or section 59 and a relatively much smaller oil- 7 cleaning compartment or section '60 having a sludge' receiving portion provided with a bottom. 62. 7

The Wall. or partition 58i's of limited height in the container or tank. Inthe embodiment shown,the oil-cleaner 39 is suspended inthe tank so that a lower'major portion is in the compartment iii], below the top of the wall 58, and the rest of the oil-cleaner, comprising an appreciable minor portion, is above the wall. The plates 40 and 42 of the oil-cleanerareparallel to the Wall 58.

When a voltage is connected across the respective series of plates 4i: and 42, an electrostatic field is established between the facing plates. Potential can. be applied to the insulated plates 42 by any conventional or suitable means which has been shown very schematically as an insulated conductor 64 passing through an insulating bushing 65 in a side of the oil tank. This coni ductor is, of course, connected to the insulated plates, and the grounded plates ib are grounded through any suitable means, such as, for example, by making the hanger hooks 48 and straps 5c of metal and connecting a grounded conductor to one or more of them.

The normal level of oil in the tank, during the times when the oil is being cleaned, is above the top edge of thewall 58. A normal oil-level close to or above the top of the plates of the oil-cleaner 39 or about an inch above the wall 58 has been found satisfactory. The space between the top edge of the Wall 58 and the cover 28 provides an opening through which oil can flow from one of the compartments 59 and 60 to the other. Stated difierently the non-restricted space immediately over the edge of the wall 58 provides for oil-communication betweenthe sections or compartments 55% and 86.

When the plates 46 and 42 are oppositely charged with a suitable direct-current energizing source and the pump 34 is deenergized, the oil in the tank very slowly and substantially imperceptibly circulates through the oil-cleaner. We are not sure whether the electrostatic field directly between facing surfaces of the plates causes oil-migration, or whether the edge-effects of the field at the edges of the plates are the cause, or both. In any event, the dirty stagnant oil in compartment bilbecomes cleaner,-with time, when the oil-cleaner is energized. Dirt dispersed in the oil is continuously electrostatically precipitated by the oil-cleaner and forms a dirt and oil layer on and along the dust-precipitating plate members of the oil-cleaner. Finally dirt or parts of the layer become too heavy and slide or drop down to the sludge-receiving section 6| in the lower part of the compartment 55. With suitable Voltage across the plates lll and 4'2, the dirt and oil layers on the oil-cleaner plates are of sludge consistency and the layer-boundaries can be clearly distinguished in the oil. The sludge accumulates in the sludge compartment and can be removed periodically in any suitable manner, as for example, through suitable valve controlled drains or outlets 68. During oil cleaning, when the container or. tank 26 holds its full alotment of oil, precipitated dirt, which is on, between or below the oilcleaning precipitating plate members 40 and 42, is prevented by the Wall 58 and plates 30 and i2 from significant remixing with oil in the clean-oil section or compartment 59.

Accordingly, the wa 53 divides the container or tank into portions, compartments or sections "59 and 60, but in such. a way that oil can move from the: oil-cleaning portion,secti'on orcompartment some the clean-oil portion, section or compartment 59 whilethe oil is being cleaned, and in such away thatcleanedoil can be withdrawn from the clean-oil portion, section or compartment 59 for circulation through the treating chamber 4.

' For air-cleanin'g applications of our invention, to which it is notlimited, it is desirable to provide' a system which is substantially automatic in its operations; Fig. 3 shows a form of electrical 'connectiorrs by which the apparatus of Fig. l may be electrically energized and auto-' matically operated. l2 and i4 represent ordinary commercialalternating current main supply conductors. One conductor '12 is connected t'oa time switch 18 which controls the connection of the conductor 32' to either of two terminals 78 or Bil. When connected to the terminal 86, the commercial power supply is applied to a power-pack 82 and to the blower motor 8 so that the electrostatic dust precipitator operates for cleaning air and for cleaning the oil' in the reservoir or tank 215'. I-Iigh-voltage direct-current potential is applied to the ionizing wires l2 by means of a 'suitable'insul'atedconductor 83, and a high-voltage direct-current potential is applied to the insulated plates l6 by means of an insulated conductor 86- in series with a current-limiting resistor 81. The insulated wire 6dbranches from the conductor 86 for applying potential to the insulated plates 42. In the described embodiment, about 12,000 volts positive is applied to the ionizing wires 12, and about 5,000 volts positive is applied to the insulated plates I6 and 42. The ground electrodes ii], the grounded plates I4, and the grounded plates 32 are grounded in any suitable manner, the ground circuit preferably including the conduit means comprising the inlet duct 2, the cabinet-duct or treating-chamber 4, the metal casing 22, and the metal container 26.

At adjustable intervals, the time switch 16 disconnects the conductor 12 from the terminal and connects it for several minutes to the terminal 78 in the energizing circuit of oil-pump motor 35. This operation stops the air flow through the precipitator and sets into operation the pumping system for pumping oil over the aircleaning elements for washing collected and accumulated dust off them. The pump-motor 35 drives the oil-pumps which withdraws oil from the cleaned-oil section or compartment 59 of the oil-reservoir, tank or container 26, through the pipe-i2. In order to inhibit or avoid significant agitation of the sludge in the bottom of the compartment 60 and the layers of dirt on the plates of the oil-cleaner, the rate at which oil moves over the submerged top edge of the wall 58 should be slow. The comparatively large length of this edge, as compared to the-diameter of the pipe 32 automatically causes the rate of flow of the oil over the wall 58 to be slower than the rate of flow of clean oil through the pipe 32. The movement of oil from the oil-cleaning portion of the container to the cleaned-oil portion of the container can be adjusted by the rate at which the oil is withdrawn and the depth of the top of the wall 58 from the normal oil level. There does not appear to be any particularly critical operation in this respect. Wide variations can be tolerated.

When the oil level is lowered below the top of the wall 58, the withdrawal of oil from the oilcleaning compartment 69 of the reservoir is effectually barred completely. The oil level is so lowered while the pump 34 is forcing oil through the system for washing the dust-collecting platis I4 and 16. The system in which oil is continuously recirculated, during operation of the pump 34, comprises an endless passage, that is, a passage that returns upon itself and is in the form of a closed or continuous loop-circuit. The passage comprises the cl an-oil section or portion 59 of the container 26, a clean-oil conduit including the inlet pipe 32 and extending to the oil-distributing nozzle means 36 in the treating-chamber 4, the nozzle means 35, the portion of the treating-chamber which includes a dust-bearing medium in the form of dust-laden plates !4 and I6 which are below the nozzle means and contaminate the oil with dust of a type normally found in air, a return conduit for contaminated oil which compris s the pan I8, the spout 29 and the ripe 39 which returns the contaminated oil back to the container. The loop-circuit includes the pump 34 which, during operation, recirculates the oil therein.

After a short time of washing, the time switch 16 deenergizes a l circuits. The pump motor is stopped and all the parts of the precipitator apparatus are deenergized During this interval,

which also may be several minutes, the oil drains from the dust-collecting plates and into the tank 25, restoring the normal oil level and fully submerging the wall 58. The time switch 16 then reconnects the conductor 12 to the terminal 80 for restarting the air-cleaning operations of the apparatus.

It will be noted that, for long periods of time, the oil is at a high level in the reservoir ortank 26, and the electrostatic oil-cleaning plate m mbers 49, 42 are energized, so that foreign matter is slowly but steadily being removed from the oil, there being sufiicient circulation or diffusion of oil above the top of the wall 58, between the compartments 59 and B9, to efiect a cleaning of substantially all of the oil in the entire reservoir 26. At intervals, however, a quantity of cleaned oil is temporarily withdrawn from the cleanedoil section or portion of the reservoir through the pipe 32. The sectionalizing wall '58 prevents the pipe 32 from withdrawing dirty oil in the oil-cleaning compartment 69 of the container or tank.

In Fig. 5, we show a somewhat modified form of tank in which an open-topped removable receptacle 89 is disposed below the oil-cleaning means, this removable receptacle having a bottom 99 from which four vertical sides extend upwardly. The open top of the receptacle is below the oil-cleaner 39 and is larger than the corresponding area of the oil-cleaner. The top is further provided with an upright wall member 99 which extends almost completely across the tank but terminates below the oil-level. A handle 9| permits the receptacle to be moved laterally or horizontally from beneath the oil-cleaner plates and then raised. Accordingly, the accumulated sludge in the receptacle 89 can be manually cleaned. out at proper intervals.

Although the embodiment of Fig. has no wall fixed inside the tank, the wall member 90 generally functions in the same manner as does the wall 58 of Fig. 1 with respect to segregating the tank into distinct portions having oil-spaces in one of which the oil is cleaned and the other of which has c1.an oil which can be used in a recirculating system. However, the wall mem-,

10 ber 99 does not completely block off oil-diffusion through any space that might be present between the vertical edges of the wall member and the side walls of the tank. For certain systems, the small additional oil-diffusion is immat:rial. It is usually desirable to keep these spaces as small as possible without interfering with the removal I and re-insertion of the receptacle 88. Otherwise, a system comprising the embodiment of Fig. 5 operates generally in a manner corresponding to that shown in Fig. 1.

A different embodiment of our invention is shown in Figs. 6 and '7. This embodiment also comprises an endless loop-circuit which includes an oil-cleaning contain r and an oil-contaminating treating-chamber connected by a clean-oil conduit and a return contaminated-oil conduit." The treating chamber contains a dust-bearing medium which is to be cleaned or washed with clean oil taken from the container.

More specifically, an oil-cleaning container or tank 92 is provided which is divid:d by a curved wall 93 into a clean-oil section 94 and an oil-' cleaning section 95. The wall 93 is fixed in the container 92 and extends for the full distancebetween the sides of the container and between the top and bottom of the container. In order to have the sections 94 and 95 in oil-commingling relation, the wall 93 is provided with a plurality of holes or openings 96, the wall 93 biing otherwise solid. Preferably, the openings 96 are in the upper portion of the wall 93 and provide the only spaces through which oil can pass between the sections 94 and 95.

The section 95 of the container 92 is provided with an oil-cleaner 91. The oil-cleaner 91 comprises a plurality of interleaved spaced electrodes 99 and 99 in the form of plates. The'horizontal length of the plates is slightly less than the corresponding dimension of the inside of the tank. The electrodes comprise a group of plates which is insulated from the remaining plates so that an oil-cleaning voltage can be applied between the two groups of pates in any suitable manner. The high-voltage plates should, of course, be properly insulated from the other plates and the container.

A sludge-receiving portion I is provided below the bottom of the electrodes 98 and 99. The clean-oil section 94 has a bottom HM, and the sludge-receiving portion I99 has a bottom I92.

The system of Fig. 6 includes a pump I03 to the intake of which a pipe I94 is connected. Pipe I04 opens. in the bottom portion of the clean-oil section 94 of the container 92. When the pump I03 operates, oil is recirculated in anendless loop-circuit. The loop-circuit comprises a clean-oil conduit including the pipe I94, the pump I93, and a pipe I connected to the outlet end of the pump I03 and to a treating chamber I96. The loop-circuit continues through the treating chamber I99, a contaminated-oil pipe I98 extending from the treating chamber I99,

and the clean-oil section 94 of the container 92 v to which the pipe Q98 is connected. The treat-v ing chamber I99 may include a dust-precipitato'rcomprising a dust-charging and dust-precipitat-r ing means along the lines of that described in. Fig. 1, or any other dust-bearing medium which is to be washed. by oil circulating in the loopcircuit.

Oil in the container 92 is cleaned in the. manner described in connection with the tank' 26 of the embodiment of Fig. 1. The wall-means 93 provides the two sections 94 and 95 in the' container 92. The. sections are in oil-commingling relation because of the openings 95, it being understood that the normal oil level of the oil in the container 92 is above the bottom of these openings. Oil is cleaned in the section 95 and cleaned oil is withdrawn from the clean-oil section 94 for circulation in the loop-circuit.

Figs. 8, 9 and 10 schematically show another modification of an oil-cleaning means in accordance with our invention. In this modification, a container, reservoir 01 tank I 22. includes a fixed wall or partition I24 which divides the tank into a clean-oil section or portion I 26 and an oilcleaning section or portion I28 in which an oilcleaner I30 is supported. Sloped walls I32 of the tank I22, below the oilcleaner I 30, provide a tank-portion I34 for sludge.

A drain at the bottom of the sludge-portion includes a valve I36 which is normally open and sludge can fall into an enlarged removable container I38 attached to the drain. The drain valve I further restricts agitation of the sludge in the sludge container I33, and prevents the sludge from being agitated when oil is being withdrawn or added, or both, to the oil-container I22 with the result that oil in the sections I25 and I28: will not become contaminated by sludge in the sludge "portion.

In the construction shown, the compartment I28 is the fu l width of the tank, but the oilcleaner I35 is spaced from the side walls I40 and I42 of the tank, in order to facilitate the migration of oil to and from the oil-cleaner. The sludge compartment I34 is of less width than the. tank, being only wide enough to span the plates of the oil-cleaner. The depth of the tank Iz22 is relatively much less than its area so that the tank is, in effect, shallow. The clean-oil section I26 of the tank, however, has a much greater area than the oil-cleaning section I28, so that an adequate supply of cleaned oil is always available.

In the modification shown in Figs. 8 through 10, the oil-cleaning electrodes of the oil-cleaner I30 are fully above the sludge-receiving compartment I 34, but are not above the wall I24. The space Over the wall I24 is open for oil flow between the sections I26 and I28 of the container.

The equipment shown in Figs. 8, 9 and 10 obviouslv can be incorporated into a svstem, such as shown in Figs. 1 and 6, and oil-cleaning is accomplished in the same general manner described in connection therewith.

In Fig. 11, we show a further embodiment in which an oil tank or reservoir I58 is provided which has no internal upstanding walls, such as the walls 58, 90, 93 and I24, of Figs. 1, 5, .6 and .8, respectively. This embodiment comprises a main compartment, section or portion I5I and a separate portion or section I 52 below the sloped bottom wall I54 of the tank. The section I52 comprises a portion I56 for receiving the oil-cleaner I58, and a portion I65, below the oil-cleaner, for receiving the sludge. This modification includes a'flat wall in the form of a closure I52 which is slidable along the top of the bottom wall. I54 for partially or fully closing the opening at the top of the portion I52 through which oil passes be. tween the portions I5I and I152; The closure is operable from the outside of the tank through onev or more shafts I64 sliding in sealing glandsaancl guides Ifi5,.and may rest .on:narrow rails across the top of portion 152.: If it: should beidesiredto completely divide the oil-cleaner and sludge com partments or portionsfrom thecleaned oil :inthe 12 remainder of the tank, the closure I62 can obviously be moved to fully closed position.

The pump I58 pumps cleaned oil through an intake pipe I10. The dirtied .oil is returned through a controllable valve I'l l in a spout III) which maybe located anywhere along thetop of thehtank I56. It is. obvious that the depth of the tank I50, the size of the portions I5.I and I52, the; construction of the oil-cleaner I58, the amount of oil in the tank, and the position of the spout I16 and closure wall I62, and the nature of the dirt collected Will determine, how much, if any, sludge will be disturbed when oil. flows into the tank.

In general, our invention is admirably suited for tanks or reservoirs in which the oil-cleaner occupies but a relatively small part of the tank or reservoir, so that the clean-oil compartment can be relatively much larger than. the other compartments. This is not always necessary, however, and in Fig. 12, a further embodiment is shown inv which an oil-cleaner I82 is in a portion or section. I82 of a tank I84, that constitutes a major portion of the tank. This embodiment further utilizes a greater number of plate-electrodes I85 -for the oil-cleaner and has a small cleaned-oil portion I88. A separate wall, such as used in the prior embodiments, is omitted between the oil-cleaning portion I82 and the clean-oil portion I83 of the tank. The portion I88 01": the tank: has a bottom I90 which is distinct from the sloped bottom I92 of the sludge-receiving portion I54 .01 the tank. An outlet I96 is provided in the lower part of a wall I198 of the tank, through which cleaned oil is withdrawn. The oil-cleaning plate-electrodes act as a barrier for preventing sludge from remixing with the oil when cleaned oil is withdrawn. From this aspect, an end plate-electrode I99, bounding the section I88, can be considered a wall. In this embodiment, the amount of cleaned oil withdrawn at any one time before the tank is replenished is usually, but not'necessarily, much less than that remaining in the tank.

An illustration of several'aspects of our invention can be gathered from tests of an embodiment including a dust-precipitator. A dust-precipitator, such as disclosed in Figs. 1 to 4, was used. It was rated to clean 1000 cubic feet of air per minute at 90 to efliciency, as measured by the Blackness or filter paper discoloration test. It was washed with .clean oil from an oil-container, tank or reservoir which contained five gallons of oil during the periods when the oil was calm and undisturbed. The operation of the equipment was such that, during pump-- ing, about three gallons of oil were in the part of the loop-circuit or oil-circulating system external to the tank 25 and about two gallons remained in the tank, the oil being withdrawn at a rate of about three gallons per minute. The dustcollecting plates 45 and 42 were kept clean with washings of once or twice a day for intervals of about eight minutes. The drainage periods were of about the same order of time or less. During air cleaning, there was no blow-off of dust from the dust-collecting plates with high velocities of 600 feet per minute, and above, of air flowing through the air-cleaner, and the air--cleaning efficiency of the equipment remained consistently high, over long periods of time.

The oil tank used in the immediately preceding tests was 9." x 1'2 x 14", and the overall dimensions of the assembly of the plates of the oilcleaner approximated 2" x 6" X 8", there being three grounded plates and two high-voltage or insulated plates, the former being negative and the latter positive. The spacing between plates was close to 1% inch. The voltage across the oil cleaning plates was that across the dust-collecting plates and 42 of the dust-precipitating zone.

When used with the electrostatic dust-precipitating equipment in which the oil is only intermittently pumped or recirculated, the voltage applied to the plates of the oil-cleaner need be only high enough to clean the oil to a suitable degree in the time intervals between oil washings of the dust-collecting members of the equipment. For such use, the voltages usually need not be higher than that obtainable from the direct-current side of the power-pack which supplies the operating voltages for the ionizing and precipitating zones of the gas-cleaning means of the equipment.

In the foregoin tests of an embodiment along the lines of Figs. 1-4, 5000 to 6000 volts direct current was used across the plates of the oilcleaner. This voltage was obtained from the power-pack terminal which supplied the voltage between the dust-collecting plates M and I6 of the dust-collecting zone II. The resultant average voltage gradient between the oil-cleaner plates was about 11,500 to 13,500 volts per inch.

In a comparative test with respect to the oilcleaning aspect of the tested equipment, dirt removed from air was added to clean SAE 20 motor oil before it was otherwise contaminated. After three hours, substantially all of the dirt was removed by the electrostatic oil-cleaner, but the oil remained cloudy. It required several more hours to remove the last traces of cloudiness. However, cloudiness or even a little dirt in the cleaned-oil is tolerable in systems for washing the dust-collecting members of an air-cleaning precipitator.

With very small equipment along the lines of that shown in Fig. 12, which lends itself readily to observation and measurements, a tank holding 12 gallons of an antifoam lubricating oil was provided. An oil-cleaner was used comprising seven grounded plates 6%"x14" and six insulated plates 6 /4xl2", the plates being spaced /8 inch. The voltage between plates was 10,000 volts. The voltage gradient between plates was about 16,000 volts per inch, and the oil-cleaner, when energized, drew less than 1 microampere. The oil was pump-ed from the tank at a rate of about 10 gallons per minute for washing dustcollecting plates in an oil-circulating loop-circuit that held two to three gallons of oil.

The electrostatic oil-cleaner, in two hours, cleaned the oil contaminated by dirt washed down from the dust-collecting plates, to an extent which required about four days of gravitational settling. Most of the oil-contained dirt was precipitated from the' whole body of the oil after three hours of electrostatic action, the cleaning being much slower after that. The cleanliness of the oil after seven hours of electrostatic cleaning was better than that obtained after nine days of gravitational settling of a sample of the same dirty oil. Comparisons were made by the blackness of filter paper treated with samples of oil under the same conditions. At 28 C. the clean oil had a viscosity of close to one poise and the collected sludge had a viscosity of close to nine poises, the sludge bein that obtained after electrostatic oil-cleaning periods in excess of three hours.

The specific gravity of the cleaned oil was 0.86

(iii

as compared to 0.95 for collected sludge. This may be the reason why it is desirable to avoid clearly visible agitation and disturbance of the oil in the oil-cleaner in the apparatus described in connection with Fig. 12. The respective electrical resistivities were 8X10 ohm inches for the cleaned oil and 4X10 ohm inches for the sludge. The sludge was so viscous at ordinary room temperatures that it is desirable to make the sides of the sludge-receiving compartments slope at least 45 to the horizontal. A slope of 60 is even better for insuring full unimpeded sludge drainage through reasonably small drainage valves. Otherwise, a removable sludge pan or a scraper may be required.

In general, the voltage across the oppositely charged plates of a given oil-cleaner may be varied through a wide range, and for plates spaced about 1% of an inch apart, cleaning can be obtained with voltages between the grounded and insulated plates of as low as 200 volts direct current, although we prefer to use a higher voltage because the higher the voltage, the better and quicker is the cleaning of the oil. The cleaning of the oil can also be hastened by increasing the effective area of the dust-precipitated plate members in the oil-cleaner, either by increasing their size or number, or both. In other words, for higher rates of oil-cleaning, higher voltages and larger areas of precipitating members are tions and conditions been fully investigated by us. However, We do know that good cleaning is obtained through a wide range of unidirectional voltage gradients, the rate of cleaning being, in general, roughly proportional to the applied voltage, increasing with increased voltage across the plates. At higher voltage gradients, the dirt deposits quickly and heavily on both thepositive and negative oil-cleaning plates. At lower voltage gradients, in the intermediate range, the dirt deposit on the positive plates is greater than that on the negative plates. For Pittsburgh air-borne dirt, the intermediate range seems to be in the neighborhood of about 4000 to 8000 volts per inch. In the low-voltage gradient range, very little dirt seems to deposit on the negative plates. In the low-voltage gradient range, there seems to be a tendency for the dirt to agglomerate between plates and then settle down. With larger voltage gradients, the dirt seems to migrate tcward a plate of the oil-cleaner and deposits on its surface or On the surface of the dirt already there. A layer of dirt builds up on the plates until the collected dirt or a part of it drcps or slides down the surface of the plates, and falls to the bottom of the sludge-receiving means. We believe that the dirt falls or slides down the plates when it ultimately becomes toe heavy for the forces tending to keep it on the plate. The building up of layers of precipitated dirt on the plates of the oil-cleaner is a factor for consideration in selecting the plate spacing and voltages. The greater the volume between the oil-cleaning plates, the more dirt can be permitted to accumulate in the space therebetween so that the capac ity of the electrostatic oil-cleaner is thereby increased.

In the use described in connection with aircleaning, to which our invention is not limited, it is desirable to use a spacing large enough to permit collected dirt to slide down the plates with an ample margin of clearance, and; before the layer builds up thick. enough to bridge the space between the facing positive and negative plates.

Dust in the general permeating atmosphere breathed by persons is usually of high electrical resistivity. In tests with some very black oil drained from an automobile crankcase, the cleaning was at a much slower rate than the cleaning of similar oil contaminated only with dirt removed from air. The dirt from an automobile crankcase. contains many low resistivity carbonaceous, metallic and. hydrated particles. It seems then that low resistivity particles are not removed from the oil as quicldy as. particles of high resistivity. It is known, of course, that low resistivity particles do not stick to a plate of an electrostatic precipitator very long, but travel back and forth between plates. Such particles, however, may tend to agglomerate, but arcing through the oil may take place, especially with higher voltage gradients, when strings of low resistivity particles line up in a direction for bridging the spacing between plates. Current drawn by the oil-cleaner in the crankcase oil was 3.7 microamperes at 5500 volts, a current much in excess of that taken by the apparatus when removing air dirt from the oil. To prevent damage because of such arcing or shorting possibilities, it may be desirable to use a protective resistor in the energizing circuit for the oil-cleaner. An example of such a resistor is shown at 299 in Fig. 8.

This application is a continuation-in-part of our application, Serial No. 544,581, filed July 12, 1944 and of our application, Serial No. 363,442, filed October 30, 1940. Both of the foregoing applications have technically become abandoned. Our application, Serial No. 603,503, filed July 6, 1945 (now Patent Number 2,448,046), describes and claims a further improved embodiment of our invention.

While we have described our invention in connection with forms now preferred by us, and have described several specific embodiments and given data in connection therewith, it is obvious that our invention is not limited thereto and that elements of the various modifications and embodiments are of more general application and in many instances an element or elements of a first embodiment can be substituted for or added to an element or elements of a different embodiment.

We claim as our invention:

1. Oil-cleaning apparatus comprising an oilreservoir adapted to normally contain oil during extended periods of time, electrical cleaningmeans occupying a relatively small, quiet portion of said reservoir, said electrical cleaning-means including electrode-means immersed in the oil and means for maintaining a unidirectional voltage on said electrode-means for slowly but steadily causing the precipitation of foreign matter from the oil in the course of an extended period of time, partition-means extending up from the bottom of said reservoir to a point below the normal oil-level therein dividing off said relatively small, quiet portion from the main part of the. reservoir, intermittently operating means for at times withdrawing ,a quantity of cleaned oil from the main part of the reservoir, and for adding a quantity of dirty oil to said main part of the reservoir.

2. Oil-cleaning apparatus comprising an oilreservoir adapted to normally contain oil during extended periods of time, electrical cleaningmeans occupying a quiet portion of said reser voir, said electrical cleaning-means including electrode-means below the normal oil level and means for maintaining a unidirectional voltage on said electrode-means for slowly but steadily causing the precipitation of foreign matter from the oil in the course of an extended period of time, partition-means extending up from the bottom of said reservoir to a point below the normal oil level therein, segregatin said quiet portion from a second portion of the reservoir, and means for withdrawing cleaned oil from said second portion of the reservoir, and for adding dirty oil to said second portion of the reservoir[ 3. Oil-cleaning apparatus comprising an oilreservoir adapted to normally contain oil during extended periods of time, electrical cleaningmeans occupying a first portion of said reservoir, said electrical cleaning-means including electrode-means immersed in the oil and means for maintaining a unidirectional voltage on said electrode-means for slowly but steadily causing the precipitation of foreign matter from the oil in the course of an extended period of time, partition-means extending up from the bottom of said first portion and having opening-means disposed at an oil-communication level above the bottom of said reservoir and below the normal oil-level in said reservoir, completel separating off said first portion from a second portion of the reservoir at all points below said oil-communcation level, and providing oil-communication between said reservoir-portions at said oilcommunication level, and a pipeline including a pump for withdrawing cleaned oil from said second portion of the reservoir, and for adding dirty oil to said second portion of the reservoir.

GAYLORD W. PENNEY. GEORGE W. HEWITT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,828,631 Whitney Oct. 20,1931 1,899,017 Dauphinee Feb. 28, 1933 2,116,509 Cottrell May 10, 1938 FOREIGN PATENTS Number Country Date 615,455 Germany July 5, 1935 

